Vertical batch furnace assembly

ABSTRACT

Vertical batch furnace assembly for processing wafers comprising a cassette handling space, a wafer handling space, and a first wall separating the cassette handling space from the wafer handling space. The first wall has at least one wafer transfer opening in front of which a wafer transfer position for a wafer cassette is provided. The cassette handling space comprises a cassette storage, and a cassette handling mechanism. The cassette storage has a plurality of cassette storage positions and is configured to store a plurality of wafer cassettes. The cassette handling mechanism comprises a first cassette handler which is configured to transfer wafer cassettes between a first set of the cassette storage positions and the wafer transfer position. The cassette handling mechanism is provided with a second cassette handler which is configured to transfer wafer cassettes between a second set of the cassette storage positions and the wafer transfer position.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationSer. No. 62/880,890, filed Jul. 31, 2019, titled VERTICAL BATCH FURNACEASSEMBLY, the disclosure of which is hereby incorporated by reference inits entirety.

FIELD OF THE DISCLOSURE

The present disclosure generally relates to a vertical batch furnaceassembly for processing wafers.

BACKGROUND

Most vertical batch furnace assemblies are provided with a cassettehandling space for receiving and storing wafer cassettes therein. Such acassette handling space is typically provided with a cassette handlingmechanism for transferring wafer cassettes between a cassette in-outport, a cassette storage and a wafer transfer position. At the cassettein-out port wafer cassettes may be exchanged between the vertical batchfurnace assembly and the cleanroom-environment in which the verticalbatch furnace assembly is accommodated. The received wafer cassettes maybe placed in the wafer transfer position from which position wafers maybe unloaded from the wafer cassette and loaded to a wafer boat forprocessing of said wafers.

The cassette storage may have a plurality of cassette storage positionson each of which a wafer cassette may be stored. The cassette storagepositions may be arranged in a storage rack, provided with for example astorage carrousel. In order to be able to reach the in-out port, thewafer transfer position and all of the wafer storage positions, atypical cassette handling mechanism may comprise an elevator mechanismand a robot arm. The elevator mechanism may provide a vertical movementof the cassette handling mechanism in order to reach the cassettestorage positions at different vertical heights. The robot arm mayprovide a two-dimensional horizontal movement in order to reach at leastsome of the storage positions.

SUMMARY

This summary is provided to introduce a selection of concepts in asimplified form. These concepts are described in further detail in thedetailed description of example embodiments of the disclosure below.This summary is not intended to identify key features or essentialfeatures of the claimed subject matter, nor is it intended to be used tolimit the scope of the claimed subject matter.

It is realized that typically a plurality of wafer cassettes may need tobe unloaded to load an entire wafer boat. It is realized that it may bedesirable to store as many wafer cassettes within the cassette handlingspace as possible. That the cassette handling space may have arectangular-shaped footprint. That elaborate cassette handlingmechanisms may be required to have sufficient reach in order to be ableto reach cassette storage positions within a cassette handling space.That the speed with which the cassette handling mechanism can transferthe cassettes within the cassette handling space, may be important forthe efficiency of the vertical batch furnace assembly.

Therefore, it may be an object to provide a vertical batch furnaceassembly of which the cassette handling mechanism has an improvedtransfer speed and/or an improved reach.

To that end, there may be provided a vertical batch furnace assemblyaccording to claim 1. More particularly, there may be provided avertical batch furnace assembly for processing wafers. The verticalbatch furnace assembly may comprise a cassette handling space, a waferhandling space, and a first wall separating the cassette handling spacefrom the wafer handling space. The first wall may have at least onewafer transfer opening in front of which, at a side of the first wallwhich is directed to the cassette handling space, a wafer transferposition for a wafer cassette may be provided. The cassette handlingspace may comprise a cassette storage, and a cassette handlingmechanism. The cassette storage may have a plurality of cassette storagepositions and may be configured to store a plurality of wafer cassettesprovided with a plurality of wafers. The cassette handling mechanism maycomprise a first cassette handler configured to transfer wafer cassettesbetween a first set of the cassette storage positions and the wafertransfer position. The cassette handling mechanism may be provided witha second cassette handler configured to transfer wafer cassettes betweena second set of the cassette storage positions and the wafer transferposition.

For purposes of summarizing the invention and the advantages achievedover the prior art, certain objects and advantages of the invention havebeen described herein above. Of course, it is to be understood that notnecessarily all such objects or advantages may be achieved in accordancewith any particular embodiment of the invention. Thus, for example,those skilled in the art will recognize that the invention may beembodied or carried out in a manner that achieves or optimizes oneadvantage or group of advantages as taught or suggested herein withoutnecessarily achieving other objects or advantages as may be taught orsuggested herein.

Various embodiments are claimed in the dependent claims, which will befurther elucidated with reference to an example shown in the figures.The embodiments may be combined or may be applied separate from eachother.

All of these embodiments are intended to be within the scope of theinvention herein disclosed. These and other embodiments will becomereadily apparent to those skilled in the art from the following detaileddescription of certain embodiments having reference to the attachedfigures, the invention not being limited to any particular embodiment(s)disclosed.

BRIEF DESCRIPTION OF THE FIGURES

While the specification concludes with claims particularly pointing outand distinctly claiming what are regarded as embodiments of theinvention, the advantages of embodiments of the disclosure may be morereadily ascertained from the description of certain examples of theembodiments of the disclosure when read in conjunction with theaccompanying drawings, in which:

FIG. 1 shows a top, partially sectional view of an example of a verticalbatch furnace assembly according to the description;

FIG. 2 shows a top, sectional view of the cassette handling space of theexample of FIG. 1; and

FIG. 3 shows a side, sectional view of another example of the cassettehandling space according to the description.

DETAILED DESCRIPTION OF THE FIGURES

In this application similar or corresponding features are denoted bysimilar or corresponding reference signs. The description of the variousembodiments is not limited to the example shown in the figures and thereference numbers used in the detailed description and the claims arenot intended to limit the description of the embodiments, but areincluded to elucidate the embodiments by referring to the example shownin the figures.

Although certain embodiments and examples are disclosed below, it willbe understood by those in the art that the invention extends beyond thespecifically disclosed embodiments and/or uses of the invention andobvious modifications and equivalents thereof. Thus, it is intended thatthe scope of the invention disclosed should not be limited by theparticular disclosed embodiments described below. The illustrationspresented herein are not meant to be actual views of any particularmaterial, structure, or device, but are merely idealized representationsthat are used to describe embodiments of the disclosure.

As used herein, the term “wafer” may refer to any underlying material ormaterials that may be used, or upon which, a device, a circuit, or afilm may be formed.

In the most general term the present disclosure may provide a verticalbatch furnace assembly 10 for processing wafers, as illustrated inFIG. 1. The vertical batch furnace assembly 10 may comprise a cassettehandling space 12 (illustrated in more detail in FIG. 2), a waferhandling space 14, and a first wall 16 separating the cassette handlingspace 12 from the wafer handling space 14. The first wall 16 may have atleast one wafer transfer opening 18 in front of which, at a side of thefirst wall 16 which is directed to the cassette handling space 12, awafer transfer position 20 for a wafer cassette 22 may be provided. Thecassette handling space 12 may comprise a cassette storage, and acassette handling mechanism 26, 28. The cassette storage may have aplurality of cassette storage positions 24 and may be configured tostore a plurality of wafer cassettes 22 provided with a plurality ofwafers. The cassette handling mechanism 26, 28 may comprise a firstcassette handler 26 configured to transfer wafer cassettes 22 between afirst set 30 of the cassette storage positions 24 and the wafer transferposition 20. The cassette handling mechanism 26, 28 may be provided witha second cassette handler 28 configured to transfer wafer cassettesbetween a second set 32 of the cassette storage positions 24 and thewafer transfer position 20.

An advantage of the above-mentioned vertical batch furnace assembly isthat each cassette handler 26, 28 is able to reach at least a part ofthe cassette storage positions 24 within the cassette handling space.There is no single robot arm which needs to be able to reach everycassette storage position. It is sufficient have the first cassettehandler 26 transfer to and from the first set 30 of cassette storagepositions 24, and the second cassette handler 28 transfer to and fromthe second set 32 of cassette storage positions 24, as long as the firstand second sets 30, 32 together include all cassette storage positions24 of the cassette storage. By choosing the location of the first andthe second cassette handler 26, 28 within the cassette handling space 12carefully with respect to the cassette storage positions 24, each canhave a limited reach while they together can still cover all cassettestorage positions 24 within the entire cassette handling space 12. Thefirst cassette handler 26 may e.g. be arranged at or near a first end ofthe cassette handling space 12, while the second cassette handler 28 maybe arranged at or near a second end of the cassette handling space 12,opposite the first end. The first set 30 of cassette storage positions24 will then cover roughly half of the cassette handling space 12 nearthe first end, while the second set 32 of cassette storage positions 24will cover roughly another half the cassette handling space 12 near thesecond end. Because both the first cassette handler 26 and the secondcassette handler 28 only need to cover roughly half of the area withrespect to a known cassette handler, the reach may be much smaller. Asmaller reach means that a less elaborate and thus a more inexpensivecassette handler may be used.

Secondly, by having two cassette handlers 26, 28 both cassette handlers26, 28 may transfer a wafer cassette towards the wafer transferposition. They may do so simultaneously. This means that while the firstcassette handler 26 is placing a wafer cassette 22 in the wafer transferposition 20, the second wafer handler 28 may already be getting anotherwafer cassette 22 from a cassette storage position 24 of the cassettestorage. By cleverly choosing where to store a wafer cassette 22 andchoosing the order in which the wafer cassettes 22 are transferred fromthe cassette storage to the wafer transfer position 20, a high overalltransfer capacity of the cassette handling mechanism 26, 28 may bereached. With such a scheme the total transfer capacity of the cassettehandling mechanism may simply be the sum of transfer capacities of thefirst and the second cassette handler 26, 28. To improve the totaltransfer capacity of the cassette handling mechanism 26, 28, thetransfer speed of both the first and second cassette handers 26, 28 onlyneeds to be more than half the transfer speed of a prior art cassettehander. A smaller transfer speed means that a less robust and thus aneven more inexpensive cassette handler may be used. Because of the lowertransfer speed, the wafer cassette 22 may also be transferred moresmoothly, reducing the risk of particle release which could damagewafers.

By using the first and the second cassette handlers 26, 28, both thereach may be improved and the transfer capacity may be increasedrelative to prior art cassette handler mechanism of vertical batchfurnaces.

In an embodiment, the first and the second cassette handler 26, 28 maybe each provided with a cassette handler arm 34, and an elevatormechanism 36. The elevator mechanism 36 may be configured to reach wafercassettes 22 placed on cassette storage positions 24 at differentvertical heights within the cassette handling space 12.

In an embodiment, the elevator mechanism 36 of the first cassettehandler 26 may be arranged on or adjacent a second wall 38 and theelevator mechanism 36 of the second cassette handler 28 may be arrangedon or adjacent a third wall 40. The second and the third wall 38, 40 maybound the cassette handling space 12 on opposite ends.

When the elevator mechanisms 36 of the first cassette handler 26 and thesecond cassette handler 28 are arranged on or adjacent opposite ends ofthe cassette handling space 12, the cassette handlers 26, 28 themselvesare also arranged on or adjacent opposite ends of the cassette handlingspace 12. The first and second set 30, 32 of cassette storage positionswill then also be arranged on or adjacent opposite ends of the cassettehandling space 12. The first set 30 of cassette storage positions 24 maybe arranged on or adjacent the second wall 38, while the second set 32of cassette storage positions 24 may be arranged on or adjacent thethird wall 40. The first set 30 of cassette storage positions 24 willcover roughly half of the cassette handling space 12, nearest the firstend, while the second set 32 of cassette storage positions 24 will coverroughly another half the cassette handling space, nearest the secondend. Because both the first cassette handler 26 and the second cassettehandler 28 only need to cover roughly half of the area with respect to aknown cassette handler, the reach of each may be much smaller. A smallerreach means that a less complicated and robust cassette handler 26, 28may be feasible which is beneficial in view of a manufacturing costs.

In an embodiment, the cassette storage may be configured to store 10 to50 wafer cassettes 22. The cassette storage may e.g., be configured tostore at least 30 wafer cassettes 22. The cassette storage may also beconfigured to store at least 40 wafer cassettes 22. This means that thecassette storage has at least 40 cassette storage positons 24. Typicallyabout 50 to 250 wafers are needed to fill a wafer boat 58. Typicallythere are about 25 wafers provided in a wafer cassette 22. This meansthat typically 2 to 10 wafer cassettes 22 are needed to fill one waferboat 58. By having at least 40 cassette storage positions 24, enoughwafer cassettes 22 may be stored to fill at least two wafer boats 58, inparticular approximately four wafer boats. Thus the loading andunloading of wafer cassettes 22 to and from the cassette handling space12 can be postponed for quite some time while the vertical batch furnaceassembly 10 is processing the wafers from the wafer cassettes 22 whichare stored in the cassette handling space 12.

In an embodiment, the wafer cassettes 22 may be embodied as FrontOpening Unified Pods (FOUP's). FOUP's are standardized wafer cassettesfor wafers in the industry. Using FOUP's is advantageous forexchangeability of the wafer cassettes 22 between the vertical batchfurnace assembly 10 and other wafer processing machines.

In an embodiment, the vertical batch furnace assembly 10 may furthercomprise at least one cassette in-out port 42, 44 provided in a wall 16,38, 40, 46 bounding the cassette handling space 12. This may be thealready mentioned first, second or third walls 16, 38, 40, but it mayalso be a distinct fourth wall 46. The cassette handling mechanism 26,28 may be configured to additionally transfer wafer cassettes 22 to andfrom the at least one cassette in-out port 42, 44. The at least onecassette in-out port 42, 44 may provide the entrance to and the exitfrom the vertical batch furnace assembly 10, for the exchange of wafercassettes 22 between the vertical batch furnace assembly 10 and theoutside world, in particular the clean room environment.

The at least one cassette in-out port 42, 44 may comprise a first and asecond cassette in-out port 42, 44 in the fourth wall 46 which may boundthe cassette handling space 12 at an end opposite the first wall 16. Thefirst cassette in-out port 42 may be reachable by the first cassettehandler 26. The second cassette in-out port 44 may be reachable by thesecond cassette handler 28.

By associating both the first and second cassette in-out ports 42, 44with respectively the first and second cassette handlers 26, 28, andthus with the first and second sets 30, 32 of cassette storage positions24, a clear separation is made within the cassette handling space 12.Each of the cassette handlers 26, 28 may have its own in-out port 42, 44and cassette storage positions 24. This means they can operateindependently of each other, without needing to wait for each other orget in each others way. This may improve the efficiency of the handlingof the wafer cassettes 22 within the cassette handling space 12.

In an embodiment, the vertical batch furnace assembly 10 may comprisestorage racks 48, illustrated in FIG. 3, which have at least a part ofthe cassette storage positions 24. The storage racks 48 may have all ofthe cassette storage positions 24. The cassette handling space 12 may beaccessible via a closeable maintenance opening via which at least onestorage rack 48 is removable from the cassette handling space 12.

A storage rack 48 is basically a rack of shelves on which wafercassettes 22 may be placed. It is a basic design without moving parts.By arranging the wafer cassettes 22 on the storage racks 48 enoughcassette storage positions 24 may be created. When such a storage rack48 is removable from the cassette handling space 12, it may simply beremoved by e.g. a hand truck, when such a removal would be necessary ordesired. One or more storage rack(s) 48 could for example be removed togive service personnel easy access to e.g., the first wall 16 at which acassette door opener device 54 may need maintenance. The cassettehandler arm 34 of the second cassette handler 28 may for example bemoved in an upper position by means of the elevator mechanism 36 so thatthe service personnel may pass under the cassette handler arm 34. Forexample by removing three storage racks 48 from the area that holds thesecond set 32 of the cassette storage positions 24, easy access to thecassette door opener device 54 may be obtained.

In an embodiment, the vertical batch furnace assembly 10 may be providedwith a substantially rectangular footprint having two opposite shortsides defining a width 50 of the vertical batch furnace assembly 10 andhaving two opposite long sides defining a length 52 of the verticalbatch furnace assembly 10. The width 50 of the vertical batch furnaceassembly 10 may be 2.2 meter or less or preferably 1.7 meter or less.The length 52 of the vertical batch furnace assembly 10 may be 5 meteror less, preferably 4 meter or less.

By having a substantial rectangular footprint, multiple vertical batchfurnace assemblies 10 may be arranged adjacent to each other, thusmaking optimal use of available floor area. Adjacent vertical batchfurnace assemblies 10 with rectangular footprints may have no unusedspace in between them. A width 50 of less than 2.2 meter is beneficialin view of interchangeability with other vertical batch furnaceassemblies, for example from other manufacturers/brands. A length 52 of5 meter or less, preferably 4 meter or less, is beneficial for reducingthe footprint altogether.

In an embodiment, the vertical batch furnace assembly 10 may comprise acassette door opener device 54. The cassette door opener device 54 maybe placed at or near the wafer transfer position 20. The cassette dooropener device 54 may be arranged on the first wall 16. The cassette dooropener device 54 may be configured to open a cassette door of a wafercassette 22 which is placed in the wafer transfer position 20. Thecassette door opener device 54 may thus automatically open a cassettedoor of a wafer cassette 22 which is placed in the wafer transferposition 20.

In an embodiment, the vertical batch furnace assembly 10 may furthercomprise a wafer handler 56, a process chamber 60, and a wafer boathandling device positioned under the process chamber 60. The waferhandler 56 may be positioned in the wafer handling space 14 and may beconfigured to transfer wafers between a wafer cassette 22 in the wafertransfer position 20 and a wafer boat 58. The process chamber 60 may beconfigured to process wafers accommodated in the wafer boat 58. Thewafer boat handling device may be positioned adjacent the wafer handlingspace 14. The wafer boat handling device may be provided with the waferboat 58 in a wafer boat transfer position, and may be configured totransport the wafer 58 boat to the process chamber 60, and to the waferboat transfer position.

When the wafer boat 58 is in the wafer boat transfer position, the waferhander 56 may transfer unprocessed wafers from a wafer cassette 22 inthe wafer transfer position 20 to the wafer boat 58, and transferprocessed wafers from the wafer boat 58 to the wafer cassette 22 in thewafer transfer position 20. When the wafer boat 58 is loaded with one ormore wafers, the wafer boat handling device may transport the loadedwafer boat 58 to the process chamber 60. In the process chamber 60 thewafers may be processed. After processing, the wafer boat handlingdevice may transport the processed wafer boat 58 from the processchamber 60 back to the wafer boat transfer position, in which positionthe wafer hander 56 may transfer the processed wafer or wafers from thewafer boat 58 to a wafer cassette 22 in the wafer transfer position 20and transfer unprocessed wafers from the wafer cassette 22 in the wafertransfer position 20 to the wafer boat 58, thus completing a batchprocess of the vertical batch furnace assembly 10.

In an embodiment, the first set 30 and the second set 32 of the cassettestorage positions 24 may be different. This means that the first set 30and the second set 32 of the cassette storage positions 24 are not equalsets and do not overlap. The first set 30 and the second set 32 may bedisjoint sets. Alternatively, they may also be overlapping sets. Theadvantage of disjoint sets is that each cassette storage positon 24 isassociated with only one cassette handler 26, 28. This will minimize theinterference between the two cassette handlers 26, 28 which may increasethe efficiency and reliability of the cassette handlers 26, 28, and maylessen the chance of break downs.

In an embodiment, the cassette storage may be provided with a rotatablecassette storage carousel having at least a part of the cassette storagepositions 24. The cassette storage carousel may comprise a centralvertical support which is rotatable around a vertical carousel axis. Thecassette storage carousel 18 may also comprise a number of platformstages connected to the central vertical support and having the cassettestorage positions 24. The cassette storage carousel may further comprisea drive assembly which may be operatively connected to the centralvertical support for rotating the central vertical support with thenumber of platform stages around the vertical carousel axis. Such acassette storage carousel is an effective way to store wafer cassettes22 in a limited space. Because the platform stages are rotatable, thecassette storage carousel may rotate unused or unoccupied cassettestorage positions 24 in the general direction of an associated cassettehandler 26, 28. The cassette handler 26, 28 may thus always place awafer cassette on the nearest cassette storage position 24. The cassettehandlers 26, 28 thus can suffice with a smaller reach than would beneeded if the cassette handler 26, 28 were to reach all cassette storagepositions 24 by itself.

Although illustrative embodiments of the present invention have beendescribed above, in part with reference to the accompanying drawings, itis to be understood that the invention is not limited to theseembodiments. Variations to the disclosed embodiments can be understoodand effected by those skilled in the art in practicing the claimedinvention, from a study of the drawings, the disclosure, and theappended claims.

Reference throughout this specification to “one embodiment” or “anembodiment” means that a particular feature, structure or characteristicdescribed in connection with the embodiment is included in at least oneembodiment of the present invention. Thus, the appearances of thephrases “in one embodiment” or “in an embodiment” in various placesthroughout this description are not necessarily all referring to thesame embodiment.

Furthermore, it is noted that particular features, structures, orcharacteristics of one or more of the various embodiments which aredescribed above may be used implemented independently from one anotherand may be combined in any suitable manner to form new, not explicitlydescribed embodiments. The reference numbers used in the detaileddescription and the claims do not limit the description of theembodiments nor do they limit the claims. The reference numbers aresolely used to clarify.

LEGEND

-   10—vertical batch furnace assembly-   12—cassette handling space-   14—wafer handling space-   16—first wall-   18—wafer transfer opening-   20—wafer transfer position-   22—wafer cassette-   24—cassette storage position-   26—first cassette handler-   28—second cassette handler-   30—first set (of cassette storage position)-   32—second set (of cassette storage position)-   34—cassette handler arm-   36—elevator mechanism-   38—second wall-   40—third wall-   42—first cassette in-out port-   44—second cassette in-out port-   46—fourth wall-   48—storage rack-   50—width-   52—length-   54—cassette door opener device-   56—wafer handler-   58—wafer boat-   60—process chamber

1. A vertical batch furnace assembly for processing wafers comprising: acassette handling space; a wafer handling space; a first wall separatingthe cassette handling space from the wafer handling space and having atleast one wafer transfer opening in front of which, at a side of thefirst wall which is directed to the cassette handling space, a wafertransfer position for a wafer cassette is provided; wherein the cassettehandling space comprises: a cassette storage having a plurality ofcassette storage positions and configured to store a plurality of wafercassettes provided with a plurality of wafers; and a cassette handlingmechanism comprising a first cassette handler configured to transferwafer cassettes between a first set of the cassette storage positionsand the wafer transfer position, wherein the cassette handling mechanismis provided with a second cassette handler configured to transfer wafercassettes between a second set of the cassette storage positions and thewafer transfer position.
 2. The vertical batch furnace assemblyaccording to claim 1, wherein the first and the second cassette handlerare each provided with a cassette handler arm, and an elevator mechanismconfigured to reach wafer cassettes placed on cassette storage positionsat different vertical heights within the cassette handling space.
 3. Thevertical batch furnace assembly according to claim 2, wherein theelevator mechanism of the first cassette handler is arranged on oradjacent a second wall and the elevator mechanism of the second cassettehandler is arranged on or adjacent a third wall, wherein the second andthe third wall bound the cassette handling space on opposite ends. 4.The vertical batch furnace assembly according to claim 1, wherein thecassette storage is configured to store at least 30 wafer cassettes. 5.The vertical batch furnace assembly according to claim 1, wherein thecassette storage is configured to store at least 40 wafer cassettes. 6.The vertical batch furnace assembly according to claim 1, wherein thewafer cassettes are embodied as Front Opening Unified Pods (FOUP's). 7.The vertical batch furnace assembly according to claim 1, furthercomprising at least one cassette in-out port provided in a wall boundingthe cassette handling space, wherein the cassette handling mechanism isconfigured to additionally transfer wafer cassettes to and from the atleast one cassette in-out port.
 8. The vertical batch furnace assemblyaccording to claim 7, wherein the at least one cassette in-out portcomprises a first and a second cassette in-out port in a fourth wallwhich bounds the cassette handling space at an end opposite the firstwall, wherein the first cassette in-out port is reachable by the firstcassette handler and wherein the second cassette in-out port isreachable by the second cassette handler.
 9. The vertical batch furnaceassembly according to claim 1, comprising storage racks which include atleast a part of the cassette storage positions, wherein the cassettehandling space is accessible via a closeable maintenance opening viawhich at least one storage rack is removable from the cassette handlingspace.
 10. The vertical batch furnace assembly according to claim 1,provided with a substantially rectangular footprint having two oppositeshort sides defining a width of the vertical batch furnace assembly andhaving two opposite long sides defining a length of the vertical batchfurnace assembly, wherein the width of the vertical batch furnaceassembly is 2.2 meter or less.
 11. The vertical batch furnace assemblyaccording to claim 10, wherein the width of the vertical batch furnaceassembly is 1.7 meter or less.
 12. The vertical batch furnace assemblyaccording to claim 10, wherein the length of the vertical batch furnaceassembly is 5 meter or less, or 4 meter or less.
 13. The vertical batchfurnace assembly according to claim 1, wherein for each wafer transferopening the vertical batch furnace assembly comprises: a cassette dooropener device configured to open a cassette door of a wafer cassettewhich is placed in the wafer transfer position.
 14. The vertical batchfurnace assembly according to claim 1, wherein the vertical batchfurnace assembly further comprises: a wafer handler positioned in thewafer handling space and configured to transfer wafers between a wafercassette in the wafer transfer position and a wafer boat; a processchamber configured to process wafers accommodated in the wafer boat; anda wafer boat handling device positioned under the process chamber andadjacent the wafer handling space, wherein the wafer boat handlingdevice is provided with the wafer boat in a wafer boat transferposition, and is configured to transport the wafer boat to the processchamber, and to the wafer boat transfer position.
 15. The vertical batchfurnace assembly according claim 1, wherein the first set and second setof the cassette storage positions are different.
 16. The vertical batchfurnace assembly according to claim 1, wherein the cassette storage isprovided with a rotatable cassette storage carrousel having at least apart of the cassette storage positions.